Recent studies has shown that compounds having the general formula Mn+1AXn exhibit unusual and exceptional mechanical properties as well as advantageous electrical thermal and chemical properties. Despite having high stiffness these compounds are readily machinable, resistant to thermal shock, unusually damage tolerant, have low density and are thermodynamically stable at high temperatures (up to 2300° C. in vacuum). M is a transition metal or a combination of transition metals, n is 1, 2, 3 or higher, A is a group A element or a combination of a group A element, and X is Carbon, Nitrogen or both. Group A element is any of a list: Aluminium Al, Silicon Si, Phosphor P, Sulfur S, Gallium Ga, Germanium Ge, Arsenic As, Cadmium Cd, Indium I, Tin Sn, Thallium Tl, Lead Pb. Transition metal M is any of a list: Scandium Sc, Titanium Ti, Vanadium V, Chromium Cr, Zirconium Zr, Niobium Nb, Molybdenum Mo, Hafnium Hf, Tantalum Ta. Mn+1AXn compounds have layered and hexagonal structures with Mn+1Xn layers interleaved with layers of pure A and this is an anisotropic structure which has exceptionally strong M-X bonds together with weaker M-A bonds, which gives rise to their unusual combination of properties.
Mn+1AXn compounds are characterized according to the number of transition metal layers separating the A-group element layers: in 211 compounds there are two such transition metal layers, on 312 compounds there are three and on 413 compounds there ore four. 211 compounds are the most predominant, these comprise Ti2AlC, Ti2AlN, Hf2PbC, Nb2AlC, (NB,Ti)2AlC, Ti2AlN0,5C0,5, Ti2GeC, Zr2SnC, Ta2GaC, Hf2SnC, Ti2SnC, Nb2SnC, Zr2PbC and Ti2PbC. The only known 312 compounds are Ti3AlC2, Ti3GeC2 and Ti3SiC2. Ti4AlN3 and Ti4SiC3 are the only 413 compounds known to exist at present. A large number of solid solution permutations and combinations are also conceivable as it is possible to form solid solutions on the M-sites, the A-sites and the X-sites of these different phases.
The Mn+1AXn compounds can be in ternary, quaternary or higher phases. Ternary phases has three elements, i.e. Ti3SiC2, quaternary phases has four elements i.e. Ti2AlN0.5C0.5, and so on. Thermally, elastically, chemically and electrically the ternary phases, quaternary phases or higher phases share many of the attributes of the binary phases.
Michel Barsoum has synthesized, characterized and published data on the Mn+1AXn phases named above in bulk form [“The Mn+1AXn Phases: A New class of Solids”, Progressive Solid State Chemistry, Vol. 28 pp 201-281, 2000]. His measurements on Ti3SiC2 show that it has a significantly higher thermal conductivity and a much lower electrical resistivity than titanium and, like other Mn+1AXn phases, it has ability to contain and confine damage to small areas thus preventing/limiting crack propagation through the material. Its layered structure and the fact that bonding between the layers is weaker than along the layers (as in graphite) give rise to a very low friction coefficient, even after six months exposure to atmosphere.
The research groups of Prof. Lars Hultman at Linköping University and Prof. Ulf Jansson at Uppsala University have demonstrated that magnetron sputtering process (a sort of Physical Vapor Deposition, PVD) can be used to deposit coatings of Ti3SiC2 and other Mn+1AXn phases onto various substrates at relatively low temperatures (approximately 750-1000° C.) [Palmquist, J.-P., et al., “Magnetron sputtered epitaxial single-phase Ti3SiC2 thin films”. Applied Physics Letters, 2002. 81: p. 835; Seppänen, T., et al. “Structural characterization of epitaxial Ti3SiC2 FILM”, in Proc. 53rd Annual Meeting of the Scandinavian Society for Electron Microscopy, Tampere, Finland 12-15 Jun., 2002 (Ed. J. Keränen and K. Sillanpää, University of Tampere, Finland, ISSN 1455-4518, 2002), p. 142-143.]
A contact element in an electrical contact arrangement may have many different applications. The contact element is used for making an electric contact to a contact member for enabling an electric current to flow between said element and said contact member. The contact element comprises a body having at least a contact surface thereof coated with a contact layer to be applied against said contact member. A sliding electric contact arrangement comprising two contact surfaces adapted to be applied to each other for establishing an electric contact may slide with respect to each other when establishing and/or interrupting and/or maintaining the contact action. Such electric contact elements, which may establish sliding contacts or stationary contacts has preferably a body made of for instance copper or aluminum.
The contact layer is arranged for establishing a contact to the contact member with desired properties, such as a low contact resistance and low friction coefficient with respect to the material of the contact member to be contacted etc. Such applications are for instance for making contacts to semiconductor devices for establishing and interrupting electric contact, in mechanical disconnections and breakers and for establishing and interrupting electric contacts in contact arrangements of plug-in type. Such electric contact elements, which may establish sliding contacts or stationary contacts has preferably a body made of for instance copper or aluminium.
An example of a contact element including a contact layer, such as a continuous film of a multielement material having strong bonds, such as covalent or metallic bonds, within each atomic layer and weaker bonds, through longer bonding distance or for example as van der Waals bonds or hydrogen bonds, between at least some adjacent atomic layers thereof is given in WO01/41167. The multielement material is MoS2, WS2 or of any layered ternary carbides and layered nitrides that can be described as M3AX2. A problem with the described multielement material is that methods to produce the material are carried out at high temperatures (700-1400° C.). This means that an electrical electric contact element, which has a body made of a material that is not shape resistant at high temperatures, for instance copper or aluminum cannot be made use of.